Ultrasonic wave transmitter receiver

ABSTRACT

A trawl net ( 2 ) is attached to ends of warps ( 4 ) extending from a ship ( 6 ), such as a trawl boat, in the sternward direction, and a transponder ( 5 ) to transmit a response signal is attached to an upper part of a net mouth of the trawl net ( 2 ). The ship ( 6 ) forms a transmission beam TB of a detection signal by a transducer ( 1 ) at the bottom of the ship, and performs detection in the detection range. The transponder ( 5 ) receives the detection signal, and forms a transmission beam TPB of a frequency different from that. A detection image and a position display image of the transponder are superposed and displayed on a display of a scanning sonar or are displayed side by side.

TECHNICAL FIELD

The present invention relates to an ultrasonic transmitting andreceiving system for detecting underwater objects by transmitting andreceiving ultrasonic waves.

BACKGROUND ART

For example, in a trawling method, a scanning sonar is effectively usedto search for a fish school to be found, tracked and captured. With asearch for a fish school, although detectability varies depending on thesize of the fish school, a school of sardine or herring, for example,can be searched from several hundred to several thousand meters away.When a fish school is found, fish tracking is performed by turning orcontrolling a ship so that the fish school is positioned in the bowdirection of the ship, and after catching up with the fish school andrunning just upon the fish school, the fish school is captured by beingdriven into a backward trawl net of the ship as the ship runs. At thattime, the point is how the net mouth of the trawl net is suitably guidedto the fish school.

The position and depth of the net mouth can be controlled by shiphandling and towing speed. However, for that purpose, the position andspeed of the net mouth have to be grasped accurately. Accordingly, inthe trawling fishing method, it is not too much to say that the fishingefficiency depends on the performance of an apparatus for monitoring theposition and depth of the net mouth.

Hitherto, the position and depth of the net mouth can be monitored by amethod in which a transponder is attached to the net mouth, a responsesignal of the transponder is received by two or three wave receiversattached to the bottom of the ship, and a phase difference of thosereceived signals is obtained to know the direction of the transponder,that is, the direction of the net mouth. Besides, JP-B-1-53751 (patentdocument 1) or JP-UM-B-5-2874 (patent document 2) disclose a system inwhich a scanning sonar is used, plural transponders are provided at thecenter of a net, and a fish school signal (echo) and a net positionsignal using the same frequency are displayed in a superposition state.

In the former method using the phase difference measurement, signalsreflected by the sea surface or the sea bottom and through multi-passroutes are mixed to the direct wave from the transponder, and there hasbeen a defect that a wrong direction is erroneously detected or positiondetection is difficult to perform stably. Besides, in the systemdisclosed in patent document 1 or 2, there have been following problemsto be solved.

First, with respect to the detection of the transponder, the systemdisclosed in patent document 2 requires another display device dedicatedto the transponder for displaying the echo signal. Besides, in order todetect the frequency, specific units such as a pressure sensor and a VFconversion circuit are required. Further, since the transponder isdetected by a vertically wide beam, there has also been a problem that ahigh SN ratio can not be obtained. In the system disclosed in patentdocument 1, there has been a problem that it is impossible todistinguish between the echo signal and the response signal of thetransponder since their frequencies are the same. Besides, with respectto both systems disclosed in patent documents 1 and 2, when thereceiving frequency band is made narrow in order to raise the detectionprobability of the response signal of the transponder, the influence ofthe Doppler shift comes to be liable to exert. That is, the SN ratio andthe Doppler shift resistance have the relation of trade-off.

With respect to the position display of the transponder, the systemdisclosed in patent document 1 has a problem that the depth informationof the transponder is difficult to grasp.

Besides, with respect to the activation of the transponder, in thesystem disclosed in patent document 1, activation of the transponder anddetection cannot be optimized independently because they are processedin common. For example, it has been necessary that signals fortransponder activation and for detection have to be transmitted andreceived at the same tilt angle. Besides, there has been a problem thatthe sound pressure of the signal to the transponder lowers as thedistance to the transponder elongates, and, as a result, the activationof the transponder becomes difficult.

An object of the invention is therefore to provide an ultrasonictransmitting and receiving system in which the foregoing problems aresolved, a specified detection area can be detected, and a position of atransponder put in water can be certainly monitored.

DISCLOSURE OF THE INVENTION

The invention is characterized by including a sonar apparatus equippedon a ship and detecting underwater objects by a transmission beam formedwith a detection signal and at least a reception beam formed with echosignals, and a transponder in water, comprising the transpondertransmitting a response signal having a frequency band different from afrequency band of the detection signal in response to an activationsignal transmitted from the sonar apparatus and received thereby, andthe sonar apparatus including a transmission beam former fortransmitting the detection signal in a form of transmission beam, areception beam former for receiving an echo signal produced by an objectreflecting the detection signal and the response signal, and anindicator for displaying the echo signal and the response signal.

As stated above, since the transponder transmits the response signal ofthe frequency band different from the frequency band of the detectionsignal transmitted from the sonar apparatus, the echo signal and theresponse signal can be processed with these signals being distinguishedfrom each other.

Besides, the invention is characterized in that the activation signal ismade a signal having a frequency band different from the frequency bandof the detection signal. By this, the transponder can be activatedindependently of the detection by the detection signal, and detectionprocessing and transponder activation can be respectively optimized.

Besides, the invention is characterized in that the transmission beamformer includes sections for separately forming the transmission beam ofthe detection signal to a detection range and a transmission beam of theactivation signal to the transponder. By this, the detection of a fishschool or the like and the activation of the transponder can beperformed independently.

Besides, the invention is characterized in that the transmission beamformer forms the transmission beam of the activation signal to thetransponder according to an azimuth or a tilt angle from the sonar tothe transponder. By this, even the transponder existing at a verydistant place can receive the activation signal of not less than a soundpressure necessary for activation, and a usable distance of thetransponder is greatly extended.

Besides, the invention is characterized in that the transmission beamformer performs formation of the transmission beam of the detectionsignal and formation of the transmission beam of the activation signalto the transponder by one transmission and reception sequence.

By this, an update period of a detection image updated by repeatingtransmission and reception is not changed, and the detection and theactivation of the transponder can be independently processed.

Besides, the invention is characterized in that the transmission beamformer forms transmission beams to respectively perform detection in avertical plane substantially vertical to a water surface and including aposition of the transponder and in a plane having a specified tilt angleand including the position of the transponder, the reception beam formerforms reception beams in the vertical plane and the plane having thespecified tilt angle, and the indicator includes sections forcollectively displaying images of the echo signal and the responsesignal in the vertical plane and the plane having the specified tiltangle.

By this, depth information of the transponder can be easily grasped.

According to the invention, since the transponder transmits the responsesignal having the frequency different from the frequency band of thedetection signal transmitted from the sonar, the echo signal and theresponse signal are distinguished and the signal processing can beperformed.

Besides, according to the invention, since the activation signal of thetransponder is made the signal having the frequency band different fromthe frequency band of the detection signal, the transponder can beactivated independently of the detection by the detection signal, andthe detection processing and the transponder activation can berespectively optimized.

Besides, according to the invention, since the scanning sonar includesthe sections for separately forming the transmission beam of thedetection signal to the detection range and the transmission beam of theactivation signal to the transponder, the detection of a fish school orthe like and the activation of the transponder can be performedindependently.

Besides, according to the invention, since the transmission beam formerforms the transmission beam of the activation signal to the transponderaccording to the azimuth from the sonar to the transponder or the tiltangle, even the transponder existing at a very distant place can receivethe activation signal of not less than the sound pressure necessary forthe activation, and the usable distance of the transponder is greatlyextended.

Besides, according to the invention, since the formation of thetransmission beam of the detection signal to the detection range and theformation of the transmission beam of the activation signal to thetransponder are performed by one transmission and reception sequence,the update frequency of the detection image updated by repeating thetransmission/reception is not changed, and the detection and theactivation of the transponder can be independently processed.

Besides, according to the invention, since the transmission beams andthe reception beams are formed which respectively perform detection inthe plane substantially vertical to the water surface and including theposition of the transponder and in the plane having the specified tiltangle and including the position of the transponder, and there isprovided section for collectively displaying the images of the echosignals and the response signals in the vertical plane and the plane ofthe specified tilt angle, the depth information of the transponder canbe easily grasped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a positional relation among a ship, a detectionrange, and a transponder.

FIGS. 2A and 2B are views showing examples of detection images in an Hmode and position displays of a transponder.

FIG. 3 is a view showing an example in which detection images in an Hmode and a V mode and positions of a transponder are collectivelydisplayed.

FIG. 4 is a view showing an example in which a detection image in an Hmode, detection images in two directions in a V mode, and positions of atransponder in the H mode and the V mode are collectively displayed.

FIG. 5 is a perspective view showing a structural example of atransducer.

FIGS. 6A and 6B are views for explaining formation of a transmissionbeam.

FIGS. 7A, 7B, 7C, 7D, 7E and 7F are views for explaining formation of areception beam.

FIG. 8 is a view showing a relation among a transmission beam, areception beam, and a detection range.

FIGS. 9A and 9B are views showing examples of a detection range at thetime of detection in the V mode.

FIGS. 10A and 10B are block diagrams showing a structure of atransmission/reception channel of a scanning sonar and a received signalprocessing part.

FIG. 11 is a block diagram showing a structure of a transponder.

FIG. 12 is a view showing a relation of various signals among atransducer of a scanning sonar, a transponder and a target.

FIG. 13 is timing chart in a scanning sonar.

FIG. 14 is a view showing a relation of various signals among atransducer of a scanning sonar according to a second embodiment, atransponder and a target.

FIG. 15 is a block diagram showing a structure of a received signalprocessing part.

FIG. 16 is a timing chart in a scanning sonar.

FIGS. 17A and 17B are flowcharts in a scanning sonar according to athird embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

A scanning sonar according to a first embodiment will be described withreference to FIGS. 1 to 13.

FIG. 1 shows an example in which an ultrasonic transmitting andreceiving system is applied to a trawling method. Here, the ship bottomof a ship (trawl boat) 6 is provided with a transducer 1 of a scanningsonar which forms a specified transmission beam and reception beam andperforms detection in a specified detection range. A trawl net 2 istowed behind the ship 6 by warps 4. A transponder 5 is attached to a netmouth of the trawl net 2. Otter boards 3 are provided at engagementportions between the warps 4 and the trawl net 2, and the opening of thenet mouth is controlled by the towing speed of the trawl net 2 There isa case where the transponder 5 is attached to the two otter boards 3.

Besides, in FIG. 1, TB denotes an umbrella-like transmission beam. Thedetection range is formed of the transmission beam TB and a receptionbeam. When receiving a detection signal or an activation signal for thetransponder, the transponder 5 transmits a response signal in adirection along the warp 4, that is, in a direction toward the ship 6.In the drawing, TPB denotes a transmission beam of the response signal.The ultrasonic transmitting and receiving system receives the responsesignal from the transponder 5 through the transducer 1.

Search and finding of a fish school is performed in front (bowdirection) of the ship 6 in the umbrella-like detection range, andtracking is performed behind (sternward direction) the ship 6 in theumbrella-like detection range, so that the fish school to be captured bythe trawl net 2 is detected. At this time, since the warp length of thewarp 4 is, for example, 1 km, and the water depth of the trawl net 2 is,for example, approximately 100 m, a tilt angle of the transmission beamTB of the detection signal indicates almost the horizontal direction.

FIGS. 2A and 2B show display examples on a display screen of the sonar.Here, FIG. 2A shows, on its upper half, a detection image in thesternward direction of the ship, and shows, on the lower part of thescreen, a position of the transponder viewed in the same direction. Afish school, together with wharf, sea bottom, sea surface reflection,and the like, is displayed on the detection image of the upper half.Differently from the upper half detection image, only the position ofthe transponder is displayed on the lower half position display image ofthe transponder.

In this example, although the range of 180° in the sternward directionis displayed, both the detection image and the position display image ofthe transponder can be displayed in a range of 360°. In that case, theposition display of the transponder is superposed on the detection imageand they are displayed. At this time, a curve of color change inaccordance with the signal intensity is made different between thedetection image and the position display image of the transponder, sothat the position of the transponder is displayed as the image differentin color tone in the detection image. By this, the position of thetransponder in the detection image can be clearly gasped.

FIG. 2B shows an example in which a detection image and a positiondisplay of a transponder are superposed on each other and are displayed.In the figure, the upper part indicates the bow direction. In thisexample, a white position display image TP of the transponder appears onthe port quarter. An image SF1 of a fish school appears in the bowdirection, and an image SF2 of a fish school appears in the vicinity ofthe sternward transponder. In the situation as stated above, the ship issubsequently controlled so that it catches up with the fish schoolappearing as the image SF1 in the bow direction, passes through theplace just above the fish school, and drives the fish school into thetrawl net.

FIG. 3 shows an example in which both an H mode to perform detection ina substantially horizontal plane with a specified tilt angle and a Vmode to perform detection in a vertical plane are displayed together.Here, SS denotes a position of the ship. On the display screen of the Hmode, similarly to that shown in FIG. 2B, there appear a fish school SF1in the bow direction, a fish school SF2 in the sternward direction, anda position display image TP of a transponder. The display screen of theV mode is a vertical section including a straight line L in the displayscreen of the H mode. When both the image of the H mode and the image ofthe V mode are seen together, the positional relation between thetransponder (that is, the net mouth of the trawl net) and the fishschool in the depth direction can be easily grasped.

FIG. 4 shows an example in which the detection image and the position ofthe transponder are separately displayed on the same screen. Here, theupper left on the screen shows the detection image in the H mode, andthe lower left shows the detection image in the V mode. The lower rightshows the position display of the transponder in the V mode, and thepart above that shows the position display of the transponder in the Hmode. Each of straight lines L1, L2 and L3 indicates azimuths in the Hmode or a tilt angle in the V mode. The screen in the V mode indicatesthe vertical sectional image at the straight line L1, L2, L3 in the Hmode.

As stated above, when the detection image of a fish school or the likeand the position display of the transponder are displayed side by side,the position of the transponder is more clearly displayed, and therelation between them can be easily grasped.

FIG. 5 is a structural view of the transducer used for the scanningsonar. As shown in FIG. 5, the transducer 1 includes an array of pluralstage and plural row ultrasonic oscillators. This transducer 1 isinstalled on the bottom of the ship so that the axis of the cylinderbecomes vertical.

FIGS. 6A and 6B are views for explaining a transmission beam. FIG. 6Ashows the directivity of a transmission beam formed in the case wheresearch is performed in all horizontal directions. FIG. 6B shows atransmission beam formed in the case where search is performed in alldirections of a specified tilt angle. When the respective oscillatorsare driven, a delay time at a lower stage of the transducer 1 is madelonger, so that the umbrella-like transmission beam is tilted downwardby a specified angle.

FIGS. 7A, 7B, 7C, 7D, 7E and 7F are views for explaining a receptionbeam. With respect to the reception beam, oscillators of plural rowscontinuous in the circumstantial direction of the transducer 1 are usedas a set. When received signals of the oscillators of plural rowscontinuous by a predetermined number are combined, as shown in FIG. 7A,they are combined while a phase at a part closer to the center of thecontinuous plural rows is more delayed, so that as shown in FIG. 7B, thedirectionality in the horizontal direction is sharpened. Besides, adelay time is set in the stage direction of the transducer 1, so thatthe tilt angle is controlled, and the directionality in the verticaldirection is also sharpened. By this, the so-called pencil-typereception beam is formed.

FIG. 7C shows an example in which the delay time is made constant, andas shown in FIG. 7D, the reception beam is directed to the horizontaldirection. FIG. 7E shows an example in which a delay time in a lowerstage is made longer, and as shown in FIG. 7F, the reception beam istilted downward.

The umbrella-like transmission beam is formed as stated above, andreception is performed by the pencil-type reception beam at a specifiedazimuth in the transmission beam, so that detection is performed in theumbrella-like detection range.

FIG. 8 is a view showing the detection range by the transmission beamand the reception beam. Here, TB denotes an umbrella-like transmissionbeam, and RB denotes a pencil-type reception beam. With respect to theazimuth direction, the reception beam RB is formed at a resolutioncorresponding to the number of oscillators in the row direction of thetransducer 1. Besides, with respect to a distance direction, thedetection image data is sequentially formed with respect to an arbitrarysection P in the transmission beam TB at a resolution corresponding to asampling period on the time axis.

In FIG. 8, the transmission beam is directed to the horizontal (θ=90°)direction or is tilted by a specified angle therefrom, so that thedetection in the H mode is performed.

Incidentally, in the example shown in FIG. 6A or 6B, although theexample in which the umbrella-like transmission beam is formed is shown,as described later, in the case where the activation signal of thetransponder is optimized, the pencil-type transmission beam is formedfor the transponder. In that case, phase controls shown in FIGS. 7A to7F are applied at the time of transmission. That is, as shown in FIG.7A, a phase at a part closer to the center of the continuous plural rowsis more delayed and vibration is performed, so that as shown in FIG. 7B,the directionality in the horizontal direction is sharpened. Besides, adelay time is set in the step direction of the transducer 1, so that thetilt angle is controlled, and the directionality in the verticaldirection is also sharpened. By this, the pencil-type transmission beamis formed.

Although the example described above uses the transducer in which theplural oscillators are arranged on the cylindrical surface, a transducerin which plural oscillators are arranged on the whole surface of aspherical surface or a partial surface thereof may be used.

FIGS. 9A and 9B are views showing examples in which the above transduceris used and the detection in the V mode is performed. FIGS. 9A and 9Bshow detection ranges of a vertical plane having a bearing angle a withrespect to the bow of the ship indicated by an arrow. FIG. 9A shows anexample of a case where the cylindrical transducer 1 is used, and FIG.9B shows an example in which a spherical transducer 1′ is used. Asstated above, in the detection of the V mode, detection is performed inthe range extending like a fan along the vertical plane.

As stated above, the transmission beam extending like the fan along thevertical plane with the specified bearing angle a shown in FIG. 9A or 9Bis formed, and the tilt angle of the pencil-type reception beam issequentially changed at high speed along the fan shape, that is,scanning of the reception beam is performed, so that the detection ofthe V mode is performed.

FIG. 10A is a block diagram showing a structure of atransmission/reception channel of a scanning sonar. In FIG. 10A, aprogrammable transmission beam former 21 gives transmission control data(TX data) to each of transmission and reception channels. An interface11 switching-controls each drive element of a driver circuit 12 based onthe transmission control data given from the programmable transmissionbeam former 21 through the interface 20. By this, the driver circuit 12outputs a pulse width modulated transmission signal. A TX amplifiercircuit 13 amplifies the transmission signal, and drives an oscillator10 through a transmission matching circuit 14 and a transmission andreception switching circuit 15. The transmission and reception switchingcircuit 15 guides the output signal of the TX amplifier circuit 13 tothe oscillator 10 in a transmission period, and guides the signaloutputted from the oscillator 10 as a received signal to a receptionmatching circuit 16 and a preamplifier 17 in the reception period. Thepreamplifier 17 amplifies this received signal, and a band pass filter18 removes a noise component other than a frequency band of the receivedsignal. An A/D converter 19 samples the signal of the receptionfrequency band at a specified sampling period, and converts it intodigital data row.

The above portions constitute a transmission and reception channel ch1.Such transmission and reception channels the number of which is equal tothe number of the oscillators 10 are provided as indicated by ch2, ch3,. . . chN.

In the case where detection in the H mode is performed, the programmabletransmission beam former 21 generates transmission control data tocontrol the phase and weight with which each transmission and receptionchannel drives an oscillator, so that an umbrella-like transmission beamis formed at a specified tilt angle. Besides, in the case wheredetection in the V mode is performed, transmission and reception controldata is generated to control the phase and weight with which eachtransmission and reception channel drives an oscillator, so that thetransmission beam extending like the fan along the vertical plane withthe specified bearing angle α shown in FIG. 9A or 9B is formed. Further,as described later, in the case where the activation signal of thetransponder is optimized, in order to form the transmission beam of theactivation signal to the transponder, transmission control data isgenerated to control the phase and weight with which each transmissionand reception channel drives an oscillator, so that the pencil-typetransmission beam of a specified azimuth and a specified tilt angle isformed.

FIG. 10B is a block diagram of a received signal processing part whichuses the plural transmission and reception channels ch1 to chN shown inFIG. 10A to form a reception beam and performs a detection image displayin a specified detection range and a position display of thetransponder. Here, based on the reception data of the N channelsinputted from the interface 20 shown in FIG. 10A, a reception beamformer 22 performs control of phases and weights of received signals bythe respective oscillators and combines them to form the pencil beamtype reception beam at a specified azimuth, and obtains received signalsthereof. A filter 23 extracts a received signal H1 by an echo detectiontransmission and reception beam among the received signals by filtering(digital filter operation) of a band pass filter with a center frequencyof 25 kHz. Besides, a received signal H2 by a reception beam fortransponder detection is extracted by filtering of a band pass filterwith a center frequency of 24 kHz. An envelope detection circuit 24demodulates the two received signals H1 and H2 to obtain respectivesignal intensities. An image processing part 25 generates image data todisplay the detection image and the position of the transponderaccording to the signal intensities of the detected H1 and H2. A displayoperation part 26 includes a display part and an input operation part ofa user interface, reads the operation content of an operator from acontrol part 27, and performs an image display based on a signaloutputted from the image processing part 25. Besides, the displayoperation part 26 controls the respective parts shown in FIG. 10B. Forexample, setting of a tilt angle θ of a detection range at the time ofdisplay in the H mode, or a bearing angle a with respect to the bow ofthe ship at the time of display in the V mode, switching of the displaymode and the like are performed.

FIG. 11 is a block diagram showing a structure of a transponder. Here,an oscillator 30 receives a detection signal or an activation signalfrom a sonar, and transmits a response signal. A transmission andreception switching circuit 36 is on standby in a normal reception mode,and gives a received signal by the oscillator 30 to a preamplifier 31.The preamplifier 31 amplifies this, and a band pass filter 32 allows asignal of a specified band with a center frequency band (25 kHz) fortransponder activation to pass through. A control circuit 33 activates apulse generation circuit 34 when an output signal of the band passfilter 32 exceeds a specified threshold. The pulse generation circuit 34generates a tone burst wave of 24 kHz as a response signal. Atransmission circuit 35 amplifies this, and switches the transmissionand reception switching circuit 36 to the transmission side to drive theoscillator 30. By this, the response signal is transmitted.

FIG. 12 shows a relation of transmission and reception signals among atransducer of a scanning sonar, a transponder, and a target such as afish school. A detection signal f1 of 25 kHz is transmitted from thetransducer of the scanning sonar. The transponder is activated byreceiving this, and transmits a response signal f2 of 24 kHz. The targetpassively reflects the detection signal f1. By this, the transducer ofthe scanning sonar receives signals in which the echo signal f1 and theresponse signal f2 of the transponder are spatially superposed on eachother.

FIG. 13 shows a timing chart at the time of detection operation of thescanning sonar. In FIG. 13, a “transmission signal” typically indicatesa drive waveform (transmission signal) given to one oscillator of pluraloscillators of the transducer. In this example, the detection signal f1(25 kHz) is outputted.

“Reception A/D data” is time series data converted by the A/D converter19 shown in FIG. 10A. In a reception beam formation period, the timeseries data from each channel is processed.

In “RXBMF output”, a reception beam to receive echo detection and aresponse signal of the transponder is formed by the processing of theprogrammable reception beam former 22 shown in FIG. 10B. In thisexample, the reception beam for echo detection and transponder detectionis formed of 64 beams.

In “filter output”, frequency filtering of 25 kHz for an echo detectionmode (H1 mode) and frequency filtering of 24 kHz for a transponderdetection mode (H2 mode) are performed.

In “drawing processing”, with respect to the detection signal and theresponse signal obtained in this way, an envelope is detected by theenvelope detection part 24 shown in FIG. 10B, image data of thedetection signal and image data of the response signal are respectivelygenerated in the image processing part 25, and they are displayed on thedisplay operation part 26.

The above transmission beam formation period and the reception beamformation period subsequent thereto are made one transmission andreception sequence, and this is repeated.

Next, a scanning sonar according to a second embodiment will bedescribed with reference to FIGS. 14 to 16.

In the example described above, although the example has been describedin which the detection signal is used also as the activation signal ofthe transponder, an example in which the activation signal of thetransponder is made a signal of a frequency different from the detectionsignal will next be described.

FIG. 14 shows a relation of transmission and reception signals among atransducer of a scanning sonar, a transponder and a target such as afish school in that case. A detection signal f1 of 25 kHz and anactivation signal f4 of 26 kHz are transmitted from the transducer ofthe scanning sonar. The transponder is activated by receiving this andtransmits a response signal f3 of 27 kHz. The target passively reflectsthe detection signal f1. By this, the transducer of the scanning sonarreceives signals in which the echo signal f1 and the response signal f3of the transponder are spatially superposed on each other.

FIG. 15 is a block diagram showing a structure of a received signalprocessing part in this case. The structure of each transmission andreception channel and a transmission beam former is similar to thatshown in FIG. 10A. However, the transmission beam former forms thetransmission beam for transponder activation in addition to thetransmission beam for echo detection.

In FIG. 15, a reception beam former 22 forms a reception beam for echodetection, and forms a reception beam for reception of a response signalfrom the transponder. A filter 23 allows a specified band with a centerof 25 kHz to pass through with respect to the received signal H1 basedon the reception beam for echo detection, and allows a specified bandwith a center of 27 kHz to pass through with respect to the receivedsignal H2 based on the reception beam for reception of a response signalfrom the transponder. The others are the same as those shown in FIG.10B.

FIG. 16 shows a timing chart at the time of detection operation of thescanning sonar. In FIG. 16, a “transmission signal” typically indicatesa drive waveform (transmission signal) given to one oscillator amongplural oscillators of the transducer. In this example, a detectionsignal f1 (25 kHz) for the H mode is transmitted, and a transponderactivation signal f4 (26 kHz) is transmitted. The two signals aresuccessively transmitted in a transmission beam formation period.

“Reception A/D data” is time series data converted by the A/D converter19 shown in FIG. 10A. The time series data from each channel isprocessed during a reception beam formation period.

In “RXBMF output”, a reception beam for receiving echo detection and aresponse signal of a transponder is formed by the processing of theprogrammable reception beam former 22 shown in FIG. 10B. In the casewhere the reception beam formation capacity of the programmablereception beam former 22 is 128 beams, 64 beams of beam numbers 1 to 64are assigned to the mode (H1 mode) for echo detection, and 64 beams ofbeam numbers 65 to 128 are assigned to the mode (H2 mode) fortransponder detection.

In “filter output”, similarly to the case of the first embodiment,frequency filtering corresponding to each of the detection signal andthe response signal is performed.

In “drawing processing”, with respect to the detection signal and theresponse signal obtained in this way, an envelope is detected by theenvelope detection part 24 shown in FIG. 10B, image data of thedetection signal and image data of the response signal are respectivelygenerated in the image processing part 25, and they are displayed on thedisplay operation part 26.

The above transmission beam formation period and the reception beamformation period subsequent thereto are made one transmission andreception sequence, and this is repeated. Incidentally, since thetransmission timing of the detection signal f1 and the transmissiontiming of the transponder activation signal f4 are not simultaneous, acorrection of the time difference is performed at the time of drawingprocessing for the detection image and the position display of thetransponder.

As stated above, in the case where the activation signal of thetransponder is formed separately from the transmission beam of thedetection signal, when the activation signal is transmitted by thetransmission beam in which the beam is extended in the verticaldirection, the detection of the transponder can be easily performed.

Incidentally, according to the method of generating the signal fortransponder activation separately from the signal for echo detection asstated above, a modulation wave such as, for example, FM, PSK or FSK maybe transmitted as the transponder activation signal. By that, themixture of the activation signal of the transponder and the echodetection signal can be further suppressed. Besides, the transponder maytransmit a modulation wave, such as FM, PSK or FSK, as the responsesignal. By that, the mixture of the response signal of the transponderand the echo signal can be further suppressed.

In the foregoing example, although the two transmission signals for thetransmission beam formation are transmitted in time division in thetransmission beam formation period, these may be simultaneouslytransmitted. That is, a composite signal of the detection signal f1 andthe activation signal f4 is made one burst wave and may be transmittedat once.

Besides, in the foregoing example, although the detection of an echo isperformed in the H mode, and the activation of the transponder isperformed, similarly, the detection of an echo is performed in the Vmode, and the activation of the transponder can also be performed.Further, in the H mode and the V mode, the detection of an echo and theactivation of the transponder can be performed substantially at the sametime. For example, in one transmission beam formation period, thetransmission for the echo detection and the transponder activation isformed in the H mode, and the transmission beam for the echo detectionand the transponder activation is formed in the V mode. Then, in thereception beam formation period, the reception beam for the echodetection and the transponder position detection is formed in the Hmode, and further, the reception beam for the echo detection and thetransponder position detection is formed in the V mode. As a result, asshown in FIGS. 3 and 4, the detection image display and the positiondisplay of the transponder in the H mode, and the detection imagedisplay and the position display of the transponder in the V mode can beperformed.

Next, a scanning sonar according to a third embodiment will be describedwith reference to FIGS. 17A and 17B.

In some examples described above, the transponder exists in a specifieddetection range (section), and the transponder is activated by formationof the transmission beam to the detection range. In this thirdembodiment, the position of a transponder is tracked, and the activationsignal to the transponder is optimized.

FIG. 17A shows a processing relating to a tilt angle. First, detectionimage data in a vertical plane at a specified azimuth is generated, anda position of the transponder in the vertical direction (tilt angle ofthe response signal from the transponder) is detected. Then, the tiltangle of the transmission beam of the activation signal and the tiltangle of the reception beam are made to match the tilt angle of theresponse signal. FIG. 17B shows a processing relating to an azimuth.First, detection image data in a specified substantially horizontalplane is generated, and a position of the transponder in the horizontaldirection (azimuth of the response signal from the transponder) isdetected. Then, the azimuth of the transmission beam of the activationsignal and the azimuth of the reception beam are made to match theazimuth of the response signal.

The programmable transmission beam former 21 shown in FIG. 10A giveseach transmission and reception channel the transmission control data tocontrol the phase and weight with which each transmission and receptionchannel drives the oscillator, so that the transmission beam of theactivation signal to the transponder becomes the pencil-typetransmission beam with the set azimuth and the tilt angle. Besides,based on the reception data from each transmission and receptionchannel, the reception beam former 22 controls the phases and weights ofthe received signals by the respective oscillators and combines them, sothat the pencil beam type reception beam is formed in the direction ofthe transponder, and the received signal is obtained.

Incidentally, in the example shown in FIG. 7, although the control isperformed so that both the tilt angle and the azimuth of thetransmission beam of the activation signal are directed toward thetransponder, only one of the tilt angle and the azimuth may becontrolled.

INDUSTRIAL APPLICABILITY

The invention can be used for an ultrasonic transmitting and receivingsystem for detecting underwater objects by transmitting and receivingultrasonic waves.

1. An ultrasonic transmitting and receiving system comprised with asonar apparatus equipped on a ship and detecting underwater objects by atransmission beam formed with a detection signal and at least areception beam formed with echo signals, and a transponder in water,comprising: the transponder transmitting a response signal having afrequency band different from a frequency band of the detection signalin response to an activation signal transmitted from the sonar apparatusand received thereby, and the sonar apparatus including a transmissionbeam former for transmitting the detection signal in a form oftransmission beam, a reception beam former for receiving an echo signalproduced by an object reflecting the detection signal and the responsesignal, and an indicator for displaying the echo signal and the responsesignal.
 2. The ultrasonic transmitting and receiving system according toclaim 1, wherein the activation signal is a signal having a frequencyband different from the frequency band of the detection signal.
 3. Theultrasonic transmitting and receiving system according to claim 1 or 2,wherein the transmission beam former includes sections for separatelyforming the transmission beam of the detection signal to the detectionrange and a transmission beam of the activation signal to thetransponder.
 4. The ultrasonic transmitting and receiving systemaccording to claim 3, wherein the transmission beam former forms thetransmission beam of the activation signal to the transponder accordingto an azimuth from the sonar to the transponder or a tilt angle.
 5. Theultrasonic transmitting and receiving system according to any one ofclaims 1 to 4, wherein the transmission beam former performs formationof the transmission beam of the detection signal and formation of thetransmission beam of the activation signal by one transmission andreception sequence.
 6. The ultrasonic transmitting and receiving systemaccording to any one of claims 1 to 5, wherein the transmission beamformer forms transmission beams to respectively perform detection in avertical plane substantially vertical to a water surface and including aposition of the transponder and in a plane having a specified tilt angleand including the position of the transponder, the reception beamerforms reception beams in the vertical plane and the plane having thespecified tilt angle respectively, and the indicator includes sectionsfor collectively displaying images of the echo signal and the responsesignal in the vertical plane and the plane having the specified tiltangle.